Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)

Bukhari :: Book 5 :: Volume 59 :: Hadith 729

Narrated Anas bin Malik:

While the Muslims were offering the Fajr prayer on Monday and
Abu Bakr was leading them in prayer, suddenly Allah's Apostle
lifted the curtain of 'Aisha's dwelling and looked at them while
they were in the rows of the prayers and smiled. Abu Bakr retreated
to join the row, thinking that Allah's Apostle wanted to come out
for the prayer. The Muslims were about to be put to trial in their
prayer (i.e. were about to give up praying) because of being
overjoyed at seeing Allah's Apostle. But Allah's Apostle beckoned
them with his hand to complete their prayer and then entered the
dwelling and let fall the curtain.